title: The microtubule end-binding protein EB2 is a central regulator of microtubule reorganisation in apico-basal epithelial differentiation.
abstract: Microtubule end-binding (EB) proteins influence microtubule dynamic instability, a process that is essential for microtubule reorganisation during apico-basal epithelial differentiation. Here, we establish for the first time that expression of EB2, but not that of EB1, is crucial for initial microtubule reorganisation during apico-basal epithelial differentiation, and that EB2 downregulation promotes bundle formation. EB2 siRNA knockdown during early stages of apico-basal differentiation prevented microtubule reorganisation, whereas its downregulation at later stages promoted microtubule stability and bundle formation. Interestingly, although EB1 is not essential for microtubule reorganisation, its knockdown prevented apico-basal bundle formation and epithelial elongation. siRNA depletion of EB2 in undifferentiated epithelial cells induced the formation of straight, less dynamic microtubules with EB1 and ACF7 lattice association and co-alignment with actin filaments, a phenotype that could be rescued by inhibition with formin. Importantly, in situ inner ear and intestinal crypt epithelial tissue revealed direct correlations between a low level of EB2 expression and the presence of apico-basal microtubule bundles, which were absent where EB2 was elevated. EB2 is evidently important for initial microtubule reorganisation during epithelial polarisation, whereas its downregulation facilitates EB1 and ACF7 microtubule lattice association, microtubule-actin filament co-alignment and bundle formation. The spatiotemporal expression of EB2 thus dramatically influences microtubule organisation, EB1 and ACF7 deployment and epithelial differentiation.
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Goldspink
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Gadsby
authors.forename: Gemma
authors.initials: G
authors.lastname: Bellett
authors.forename: Jennifer
authors.initials: J
authors.lastname: Keynton
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Tyrrell
authors.forename: Elizabeth K
authors.initials: EK
authors.lastname: Lund
authors.forename: Penny P
authors.initials: PP
authors.lastname: Powell
authors.forename: Paul
authors.initials: P
authors.lastname: Thomas
authors.forename: Mette M
authors.initials: MM
authors.lastname: Mogensen
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D018938:Caco-2 Cells; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D003051:Cochlea / Q000378:metabolism; D015536:Down-Regulation; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005326:Fetal Proteins / Q000494:pharmacology; D000080865:Formins; D045325:HCT116 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism* / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000494:pharmacology; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering
chemical_list: D005326:Fetal Proteins; D000080865:Formins; C095003:MACF1 protein, human; C500985:MAPRE1 protein, human; C588005:MAPRE2 protein, human; C403664:MAPRE3 protein, human; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering
keywords: ACF7; Actin filaments; Cochlea; EB1; EB2; Epithelia; Intestinal crypt; Microtubules